The general hypothesis to be tested by this research plan is that the new 14C-2-deoxyglucose functional brain mapping technique of Sokoloff combined with high resolution computerized densitometry can be used to map changes in glucose utilization of the heart in response to stimulation of cardiac symapthetic and vagal efferent nerves in the anesthetized canine. The specific aims are: 1) to determine the level of glucose utilization in the control, beating, insitu heart including the relative differences in glucose utilization of the endocardium, myocardium and epicardium of the cardiac chamber walls in surgically prepared, cardiac paced, pentobarbital anesthetized dogs; 2) to determine the effect of cardiac sympathetic and vagal efferent stimulation on glucose utilization of specific regions of the heart as compared with control and to compare the vagally stimulated hearts with the sympathetic stimulated hearts. Fifteen dogs (5-10 kg) will be divided into three groups; one group of surgical controls; one group with left stellate stimulation; and one group with left vagal stimulation. A single bolus of 14C-2-deoxyglucose will be injected into the systemic circulation, and the appropriate stimulations will be produced intermittently for 45 minutes. The hearts will then be rapidly removed and frozen for sectioning into 20 micron thick transverse sections and prepared for autoradiography. After development, the autoradiographs will be analyzed using a high resolution (4096 shades of grey) computerized densitometer. This study will evaluate this new 14C-2-deoxyglucose mapping method and its appropriateness for cardiac function studies. If this method proves to be effective in the heart, it will spawn a host of studies that could evaluate various aspects of cardiac physiology, cardiac reflexes, cardio-active drugs and cardiac pathology. This new methodology could yield much new information about the heart which cannot be obtained using any of the existing methodology.